Did You Know? Emperor penguins vary between having darker feathers during winter (as in this drawing) and lighter, brown feathers in the warmer months. Their feathers actually play a vital part in making them energy efficient both underwater and on land. While underwater, their feathers flatten, making them more streamlined as well as waterproof and thus, less susceptible to heat loss as well. While on land, their feathers remain erect, trapping a layer of air and providing extra insulation against temperatures as low as −40 °C.